kc3-lang/libtommath/mp_xor.c

• Show log

  Commit

• Hash : bcda8fc6
  Author :
  Date : 2019-10-29T22:38:49
  

  simplifications: remove unnecessary optimization * these double checks are not necessary * the compiler will move the early return outside of the called function, basically the functions is partially inlined * however lto/amalgamation needed for the optimization

Download

• mp_xor.c

• #include "tommath_private.h"
  #ifdef MP_XOR_C
  /* LibTomMath, multiple-precision integer library -- Tom St Denis */
  /* SPDX-License-Identifier: Unlicense */
  
  /* two complement xor */
  mp_err mp_xor(const mp_int *a, const mp_int *b, mp_int *c)
  {
     int used = MP_MAX(a->used, b->used) + 1, i;
     mp_err err;
     mp_digit ac = 1, bc = 1, cc = 1;
     mp_sign csign = (a->sign != b->sign) ? MP_NEG : MP_ZPOS;
  
     if ((err = mp_grow(c, used)) != MP_OKAY) {
        return err;
     }
  
     for (i = 0; i < used; i++) {
        mp_digit x, y;
  
        /* convert to two complement if negative */
        if (a->sign == MP_NEG) {
           ac += (i >= a->used) ? MP_MASK : (~a->dp[i] & MP_MASK);
           x = ac & MP_MASK;
           ac >>= MP_DIGIT_BIT;
        } else {
           x = (i >= a->used) ? 0uL : a->dp[i];
        }
  
        /* convert to two complement if negative */
        if (b->sign == MP_NEG) {
           bc += (i >= b->used) ? MP_MASK : (~b->dp[i] & MP_MASK);
           y = bc & MP_MASK;
           bc >>= MP_DIGIT_BIT;
        } else {
           y = (i >= b->used) ? 0uL : b->dp[i];
        }
  
        c->dp[i] = x ^ y;
  
        /* convert to to sign-magnitude if negative */
        if (csign == MP_NEG) {
           cc += ~c->dp[i] & MP_MASK;
           c->dp[i] = cc & MP_MASK;
           cc >>= MP_DIGIT_BIT;
        }
     }
  
     c->used = used;
     c->sign = csign;
     mp_clamp(c);
     return MP_OKAY;
  }
  #endif
  

Download